@TCIII
Thanks for the help.
I did the changes but it did not succeed.
Reversing the inputs from pixhawk to the ESC, just reversed the problem.
In AUTO mode just one wheel moves, and in STEERING mode the wheels move in different speeds. The output voltage of Sabertooth is 3.8V in one side and 4.6V in the other.
Doo you think there are more parameters I can change to solve this issue?
Try another Sabertooth configuration?

@Andre,
I assume that you are using the PITCH input channel for Forward/Reverse and the ROLL input channel for steering right and left?
What Pixhawk servo output channels do you have the Sabertooth ESC hooked to?
Regards,
TCIII AVD